Calculating irradiance from lux of a halogen lamp

[Flucky]

Hi all. We're currently working on a project and need to know the irradiance hitting a steel sheet some distance away from a halogen lamp. The setup looks like:

The problem is we can only measure the lux at the surface of the steel sheet, and I believe in order to convert lux to irradiance you need to know the spectrum of the light coming from the lamp - something we are unable to do.

Is there any alternative way of getting a reasonably accurate irradiance measurement?

 

[Greg Bernhardt]

Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?